Refractory iron deficiency anemia and Helicobacter Pylori Infection in pediatrics: A review.

BACKGROUND
Since the discovery of Helicobacter pylori, several clinical reports have demonstrated that H. Pylori infection has emerged as a new cause of refractory iron stores in children. We carried out a systematic literature review to primarily evaluate the existing evidence on the association between childhood H. Pylori infection and iron deficiency anemia (IDA) and secondly, to investigate the beneficial effects of bacterium elimination.


MATERIAL AND METHODS
This review concerns important pediatric studies published from January 1991 to October 2014. Fourteen case reports and series of cases, 24 observational epidemiologic studies, seven uncontrolled trials, and 16 randomized clinical trials were included in the review.


RESULTS
Although there are a few observational epidemiologic studies and some randomized trials mostly due to the potential confounders, most studies reported a positive association linking between H. Pylori infection and iron deficiency or iron deficiency anemia among children. In addition, it seems that elimination of H. Pylori infection induces beneficial effects on iron deficiency.


CONCLUSIONS
Since the evidence for the association of H. pylori eradication therapy and refractory childhood IDA is not enough and there are contrasting data about such association, future high quality and cohort researches are needed to determine the causal association.


Introduction
Anemia, defined as a decrease in the amount of red blood cells (RBCs) or the amount of hemoglobin (Hb) concentration below established cut-off levels, is a global public health problem. Based on the World Health Organization (WHO) estimates, almost a quarter of the world`s population is anemic (1). Anemia occurs at all stages of the life cycle, but it is more prevalent in mothers and young children. It is estimated that 42% of pregnant women and 47% of preschool children are anemic (1). The most dramatic health consequence of severe anemia, which is well documented are increased risk of maternal and child mortality (2,3). Iron deficiency anemia caused the loss of 19.7 million disability-adjusted life years, accounting for 1.3% of the global total (4). Investigating the etiology of IDA in order to develop therapeutic strategies must be the first priority of health research agenda, especially in the developing countries. Many risk factors for IDA have been identified such as inadequate iron intake and absorption, increased iron requirements during growth, and excessive iron losses. In recent years, the association between Helicobacter Pylori (H. Pylori) infection and iron deficiency (ID) or IDA has been proposed seriously. H. Pylori is a highly prevalent microbial chronic infection across the world. Its worldwide prevalence is about 50% with a high variation related to the geography, age, and socioeconomic class. The overall prevalence is high in developing countries and lower in developed countries (5). It is estimated that 65% of children in developing countries are infected with H. pylori (6).In children, H. Pylori infection is associated with recurrent post-prandial abdominal pain, gastric dyspepsia, unexplained nausea and/or vomiting and duodenal ulcer which is the most known consequence of H. Pylori induced chronic gastritis and peptic ulcers (7). The association between H. pylori infection and IDA has been proposed since the last decade and currently attracted considerable interests (8,9). H. pylori infection could cause IDA by several probable mechanisms: increasing iron loss due to active hemorrhage secondary to H. Pylori gastritis (10, 11), autoimmune atrophic gastritis (12), gastric cancer (13), reducing iron absorption following chronic pan-gastritis (14), and iron utilization by the bacterium (15). In addition, Low gastric acid secretion results in an impaired "gastric barrier," which is associated with increased susceptibility to enteric infections, a major public health concern in the developing world (16). Two meta-analyses concluded that H. pylori eradication therapy combining with or without iron administration is more effective than merely iron administration for IDA treatment (17,18). Another meta-analysis conducted on Randomized Clinical Trials (RCTs), showed a non-significant improvement of Hb level following the eradication of H. pylori (19). Moreover, there is currently uncertainty regarding the effects of H. Pylori infection on IDA, especially sever one, and also of the H. Pylori eradication in the treatment of refractory IDA. Hence there is a need for a rigorous review to deal with aforementioned uncertainties. The aim of this study was to provide an extensive review of the available literature on decipher in order to the role of H. Pylori infection in IDA, especially in children age groups.

Materials and methods Types of studies
Eligible studies were all publications, if they examined the associations of H. Pylori infection and IDA in children. We included all descriptive, case-control and cohort studies as well as RCTs, including cluster-randomized trials, quasi-randomized trials, and pre-post intervention studies in the current research. Types of participants Those children below the age of 19 are eligible for the current study based on the United Nations Convention on the Rights of the Child which defines child as "a human being below the age of 18 years unless under the law applicable to the child, majority is attained earlier" (20). Search methods for identification of studies We included all English language computerized databases that are available to us in print or online. The full search strategies for MEDLINE and Pub Med Central are shown below. #1: "Helicobacter Pylori" OR "Helicobacter Pylori infection" [MeSH] #2: "anemia" [MeSH] #3: "iron Deficiency" OR "iron" OR "nutritional anemia" OR "microcytic hypochromic anemia"[MeSH, all subheadings] #4: "hemoglobin level" OR "hematocrit" OR "serum iron" OR "serum ferritin" OR "total iron binding capacity" [MeSH, all subheadings] #5: #2 OR #3 OR #4 #6: (#1 AND #5) Electronic searches We searched the following computerized databases: Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE using Pub Med, Cumulative Index to Nursing and Allied Health (CINAHL), PMC using Pub Med, POPLINE, LILACS, Health STAR, and System for Information on Grey Literature in Europe (Open SIGLE). Additional references were retrieved from the option of "related articles" and the published reviews of this topic. The search was restricted to manuscripts published from January 1990 to 30 December 2014. The search results were grouped into three categories: case reports and case series on the association between H. pylori infection and ID or IDA among children, epidemiologic observational or sero-epidemiological studies of this association, and studies of response to treatment to eliminate HP infection with ID or IDA among children. Using a standard format, the following data were abstracted from each study: type of study, age and sex of the participants, study design and population, sample size, results of the study, and treatment group characteristics for the intervention trials.

Case reports and case series
In 1991, the first evidence for an association between H. Pylori infection and serum iron in children was a case report which investigated a 15 years old girl suffering from anemia and concomitant H. Pylori associated chronic active hemorrhagic gastritis. Following the treatment of H. Pylori infection, her Hb values had become normal (21). The first evidence of association between H. Pylori infection and an unexplained IDA refractory to iron therapy came from another case report which described in a 7year-old child without any gastrointestinal symptoms (22). In that patient, the refractory anemia had been attributed to the micronodular antritis due to a chronic non-active H. pylori related gastritis without hemorrhage. It also explained how the bacterium interfered with iron metabolism. Since then, several other case reports and series of cases have confirmed the relationship between H. Pylori infection and IDA among children and also presented refractory anemia cases with no apparent cause other than chronic H. Pylori-associated gastritis whose anemia was reversed only after H. pylori eradication without (23)(24)(25)(26)(27)(28)(29) or with (31-34) iron supplementation (Table 1).

Observational epidemiologic studies
During last 15 years, several sero-epidemiologic studies from both developed and developing countries demonstrated an association between H. pylori infection and decreasing iron status among children. Some population-based studies highlighted the association between H. Pylori infection and decreasing ferritin concentrations (35)(36)(37)(38)(39)(40)(41)(42), whereas a number of them reported its association with decreasing level of ferritin and/or increasing prevalence of IDA among children (38,41,(43)(44)(45)(46)(47)(48)(49)(50)(51)(52) (Table 2). In an analysis of a cohort national survey of 1040 native children in Alaska, Parkinson et al. found a significant association between low serum ferritin levels and prevalence of H. pylori infection, particularly for child aged people (53). Bagget et al. confirmed the association of HP infection with ID and IDA among 688 children from the same population (45). Other large scale population-based studies from developed countries are listed in the followings: Seroepidemiologic study on 1771 children in the USA showed an association between HP infections with increased risk for IDA (38). Muhsen et al. found a lower ferritin level among 509 under 19-year-old children (40) and also association of HP infection with higher prevalence of anemia in 399 under 9 year-old children (41). Fraser et al. studied 792 adolescents in New Zealand and found a positive association of HP infection with increased risk of ID, but not anemia (49). There are also several related observational epidemiologic studies in developing countries. Choe et al. conducted two sero-prevalence study among 660 (43) and 937 (36) school aged children in South Korea. They found that the relative risk of IDA was 2.9 (95% CI, 1.5 to 5.6) for those with HP infection and a predominant ID/IDA prevalence among H. pylori-positive girls, respectively. Kiran et al. from India examined 484 samples of 5-12 years children and declared a 19% prevalence of HP infection in anemic group and 10.7% in non-anemic group, which suggested an association between HP and IDA (50). Several sero-epidemiologic studies using smaller sample size from Taiwan (37), Iran (42) and Egypt (52,54), pointed out association between HP infection and ID or IDA.  (51) were not successful in finding any significant association between sero-prevalence of HP infection and the IDA. Whereas the role of H. pylori infection in unexplained IDA has already been confirmed by huge documents, this contradiction could be explained by the occurrence of some biases, such as the study design, H. pylori diagnosis criteria, and adjustment for confounding factors.

Clinical and interventional trials
The most reliable evidence for a cause-andeffect comes from interventional trials which were identified for this review. Most of the identified studies showed that elimination of H. pylori associated with or without iron supplementation was followed by improvements in mean Hb levels, while others did not reveal such clear improvement in markers of iron deficiency ( Table 3). The first randomized controlled trial (RCT) to examine effects of H. Pylori treatment among children with refractory anemia without evidence of hemorrhage conducted by Choe et al. on 43 children with IDA in 1999 (59). They assigned 22 H. Pylori positive anemic girls to three groups: H. Pylori elimination treatment, iron supplementation only, and both elimination therapy plus iron supplementation. A significant increase in Hb level as compared with iron only group at 8 weeks after the therapy was found among patients who received eradication therapy (p = 0.0086). Choe et al gained the same result in another uncontrolled therapeutic trial on 13 patients (60). During recent 15 years, several controlled or uncontrolled trials conducted over diverse geographic areas in both developed and developing countries. For example, Ten RCTs have been conducted in China which all confirmed positive effect of H. Pylori eradication on the resolution of refractory IDA (61)(62)(63)(64)(65)(66)(67)(68)(69)(70). Other studies from Italy, Japan, Greece, Turkey, and Mexico reported that complete recovery of IDA could be achieved with HP eradication with or without iron supplementation among children infected with H. Pylori (71)(72)(73)(74)(75)(76). The most interesting study is related to an unblinded RCT conducted by Gessner et al. in Alaska, USA. The study population consisted of 219 children aged between 7-11 years having both ID and H. pylori infection (77). Briefly, patients were randomly assigned to two treatment groups: iron supplementation alone or iron supplementation with H. pylori elimination therapy. Iron status was reassessed at one, two, and 14 months after treatment ended. They reported that treatment of H. Pylori infection did not improve isolated ID or mild IDA up to 14 months after treatment initiation. Again the authors reassessed the same children 40 months after treatment and reported that the resolution of H. pylori infection for 40 months modestly reduced the prevalence of ID and substantially decreased the prevalence of IDA (78). In line with Alaska, another interesting RCT conducted by Sarker et al. in an area highly endemic for ID and H. Pylori infection, in Bangladesh. They conducted a double-blind and placebo-controlled trial to evaluate four types of treatment of iron plus H. pylori therapy, H. pylori therapy and placebo, iron supplementation and placebo, and placebo alone on 200 children (79). After 90 days of followup, they concluded that H. Pylori infection was neither a cause of IDA/ID nor a reason for the treatment failure of iron. Recently, an uncontrolled trial on 18 school aged cases of iron deficient and H. Pylori infected in Saudi Arabia reported relatively the same result (80). They use H. Pylori treatment without iron supplementation and no significant relationship was found between eradication therapy and serum ferritin. A recent well designed double-blind RCT studied 110 non-anemic, asymptomatic and H. pylori-positive children (3-10 years old) in Texas, USA (81). The participants were randomly assigned to receive H. Pylori eradication therapy plus iron supplementation, iron supplementation only, or placebo. They concluded that H. Pylori infection eradication had a significant increasing effect on serum ferritin level. The conflicting results of some of the abovementioned trials could be attributed to the age and sex distribution of the cases due to the variation in physiologic iron loss and iron requirements, variation in the duration of posttreatment follow-up, and other trial design limitations such as small sample sizes. Such conflicting results found in the trials that examined the effect of H. Pylori elimination treatment on refractory IDA in children, were reflected in the findings of a few related metaanalyses. Based on the meta-analysis conducted by Qu et al., observational studies showed an association between H. pylori and IDA among children, but analysis of RCTs did not showed a significant improvement of Hemoglobin or ferritin levels following the eradication of H. pylori among IDA children (82). Huang et al. analyzed eight RCTs (four of which were conducted in children age groups) of H. pylori elimination and iron supplementation performed in Asia, an area with a high incidence of IDA and H pylori (17). They concluded that H. pylori eradication therapy combined with iron administration was more effective than iron administration alone for the treatment of refractory IDA.

(53) USA
Population seroprevalence 1040 child ages A significant association between low serum ferritin levels and prevalence of HP infection found, particularly for children.

Choe et al. 2001 (43) South Korea
Population seroprevalence 660 School age The prevalence rates of HP -associated IDA in female athletes were higher than in the control group. The relative risk of IDA was 2.9 (95% CI, 1.5 to 5.6) for those with HP infection.

Choe et al. 2003 (36) South Korea
Population seroprevalence 937 10-18 The HP positive rate in the IDA group was 44.8% in comparison with 20.0% in the non-IDA group (p=0.001). The serum ferritin level was significantly lower in the HP infected group (p=0.0002).

Choi et al. 2003 (44) South Korea
Population seroprevalence 693 9-12 No significant differences in the sero-prevalence of HP infection and antibody titers to H. pylori were found between the IDA group and the non-anemic controls.